This invention relates to a solid-state laser device which comprises a laser medium of, for example, a slab shape and a lamp device for exciting the slab shaped medium. This invention also relates to the lamp device for use in the solid-state laser device.
A solid-state laser device of the type described, comprises a slab shaped medium having an optical axis and a pair of principal surfaces parallel to each other and to the optical axis and a lamp device. The lamp device comprises a reflector member and excitation lamps extended along the optical axis within the reflector member for optically exciting or energizing the slab shaped medium. The slab shaped medium is excited when the principal surfaces are applied with excitation light radiated from the excitation lamps. The solid-state laser device produces an output laser beam having output power when the excitation lamps are supplied with electric power.
It is required to realize a solid-state laser device having a high conversion efficiency between the electric or input power and the output power In order to achieve a high conversion efficiency, it is desirable to dispose the excitation lamps in the vicinity of the principal surfaces. However, it is impossible to dispose the excitation lamps near to the principal surfaces on realization of either a multipath type laser device or a moving slab type laser device for the reason which will be described hereunder.
In a multipath type laser device which will later be described in conjunction with a figure of the accompanying drawing, a plurality of zigzag resonance optical paths are formed in the slab shaped medium along the optical axis when the slab shaped medium is excited by the excitation lamps. Resonator mirrors corresponding to the resonance optical paths and holding mechanisms for the resonator mirrors are obstacles to dispose the excitation lamps in the vicinity of the principal surfaces. It is therefore impossible to dispose the excitation lamps near to the principal surfaces.
Description will proceed to the moving slab type laser device. In the moving slab type laser device, a slab shaped medium has an elongated width. That is, each principal surface has a wide width. Reciprocating motion of the slab shaped medium is carried out by a moving mechanism along a direction which is perpendicular to the optical axis and which is parallel to the principal surfaces. Inasmuch as the moving mechanism is an obstacle to dispose the excitation lamps in the vicinity of the principal surfaces, it is also impossible to dispose the excitation lamps near to the principal surfaces. Such a moving slab type laser device is disclosed, for example, in U.S. Pat. No. 4,555,786 by Robert L. Byer.
A conventional solid-state laser device is disclosed in U.S. Pat. No. 4,506,369 by J. M. Houston and comprises first and second excitation lamps extended along the optical axis within a reflector member and disposed in the vicinity of first and second side surfaces, respectively, which are parallel to the optical axis and which are perpendicular to the principal surfaces.
Since the excitation lamps are disposed near to the side surfaces, respectively, the Houston's device may be applicable to the multipath type laser device. However, even if the Houston's device is applied to the multipath type laser device, the Houston's device is defective in that there is a limit to elevate the conversion efficiency for the reason which will later be described hereunder. Inasmuch as the excitation lamps are disposed near to the side surfaces, respectively, the principal surfaces are not almost applied directly with the excitation light of the excitation lamps but are applied with reflected or indirect light reflected by the reflector member. As the principal surfaces are substantially applied with only the indirect light, there is a limit to elevate the conversion efficiency.
In addition, the Houston's device can not be applied to the moving slab type laser device. This is because the moving mechanism is also an obstacle to dispose the excitation lamps near to the side surfaces of the slab shaped medium.
Another conventional solid-state laser device is disclosed in U.S. Pat. No. 4,644,555 by Satoru Amano and comprises a reflector member having first and second reflector axes parallel to the optical axis and first and second arcuate internal surfaces, respectively, which are contiguous to each other and which surround the reflector axes, respectively. The reflector member further has a pair of parallel internal wall surfaces which are extended in parallel to each other from the first and the second arcuate internal surfaces towards a principal surface of the slab shaped medium.
The first and the second arcuate internal surfaces form first and second partially elliptic cylinders. The first and the second partially elliptic cylinders have first and second symmetry axes as the first and the second reflector axes, first and second inside focal lines, and first and second outside focal lines, respectively, which are farther from the principal surface than the first and the second inside focal lines, respectively.
First and second rod shaped laser media are placed on the first and the second outside focal lines, respectively, while first and second excitation lamps are positioned on the first and the second inside focal lines, respectively. Each excitation lamp not only illuminates the principal surface of the slab shaped medium in common to produce an output laser beam but also illuminates a corresponding rod shaped laser medium to produce another output laser beam.
Supposing that extension of the parallel internal wall surfaces is made along a direction perpendicular to the optical axis, each excitation lamp may be positioned far from the principal surface so as to realize the multipath type laser device. However, the Amano's device is also defective in that there is a limit to elevate the conversion efficiency for the reason which will be described hereunder.
Attention will be directed to the first excitation lamp. Inasmuch as the first excitation lamp is positioned on the first inside focal line, the first arcuate internal surface reflects the excitation light of the first excitation lamp as reflected or indirect light towards the first rod shaped laser medium located on the first outside focal line. Since the reflected or indirect light is absorbed by the first rod shaped laser medium, the principal surface is not almost applied with the reflected or indirect light reflected by the reflector member. Thus, the principal surface is substantially applied with only direct light of the excitation lamps. This is the reason why the Amano's device has a limit to elevate the conversion efficiency.